Internal power grids of wind power plants connect individual wind turbine generators of a wind power plant to a point of common coupling—the latter being the point where power is fed onto a power supply grid from the wind power plant. In order to do this correctly the impedance of the internal power grid between each of the wind turbines of the plant and the point of common coupling has to be taken into consideration.
The wind turbine experiencing the highest impedance to the point of common coupling needs to generate the highest wind turbine voltage level in order to compensate for voltage drops in the internal power grid. However, by following this approach the highest wind turbine voltage level within the plant may become dangerously close to, or even exceed, an upper voltage level with the risk of damaging the internal grid.
Moreover, a long time exposure to a low voltage level, being lower than the nominal voltage level could result in damages to the equipment. This is due to higher currents in order to keep the power level constant.
The voltage profiles of wind turbines connected to the internal power grid depend on the impedance values and the apparent power flowing through the internal power grid.
It may be seen as an object of embodiments of the invention to provide a method that ensures that:                no damage is caused to the equipment in an improved manner when compared to existing technology.        a predetermined voltage level within the wind power plant is not exceeded.        
It may be seen as a further object of embodiments of the present invention to provide an improved method which ensures that an overvoltage level and/or an undervoltage level within the wind turbine plant is not exceeded.